P. Olmeda - Academia.edu (original) (raw)
Papers by P. Olmeda
A lumped capacity heat transfer model has been developed and compared to measurements from a turb... more A lumped capacity heat transfer model has been developed and compared to measurements from a turbocharger operating on a 2.2L Diesel engine under steady and transient conditions ranging from 1000-3000rpm and 2-17bar BMEP. The model parameters have been estimated based on similar devices and this study quantifies the errors associated with this approach. Turbine outlet gas temperature prediction was improved with RMSE reduced from 29.5 o C to 13 o C. A sensitivity study showed the parameters of the heat transfer model influence gas temperatures by only ±4 o C but housing temperatures by up to 80 o C. Transient simulations showed how errors in the thermal capacitance also lead to errors. This study shows the importance of undertaking a full thermal characterisation and the need for accurate adiabatic maps in turbocharger simulations.
Nowadays turbocharging the internal combustion engine has become a key point in both the reductio... more Nowadays turbocharging the internal combustion engine has become a key point in both the reduction of pollutant
emissions and the improvement of engine performance. The matching between turbocharger and engine is difficult; some
of the reasons are the highly unsteady flow and the variety of diabatic and off-design conditions the turbocharger works
with. In present paper the importance of the heat transfer phenomena inside small automotive turbochargers will be
analyzed. These phenomena will be studied from the point of view of internal heat transfer between turbine and
compressor and with a one-dimensional approach. A series of tests in a gas stand, with steady and pulsating hot flow in the
turbine side, will be modeled to show the good agreement in turbocharger enthalpies prediction. The goodness of the
model will be also shown predicting turbine and compressor outlet temperatures. An accurate prediction of these
parameters is a key factor to make easier the design of intercooler and aftertreatment devices.
11th International Conference on Turbochargers and Turbocharging, 2014
11th International Conference on Turbochargers and Turbocharging, 2014
Multidisciplinary Journal for Education, Social and Technological Sciences, 2014
Multidisciplinary Journal for Education, Social and Technological Sciences, 2014
Volume 1B: Marine; Microturbines, Turbochargers and Small Turbomachines; Steam Turbines, 2014
Volume 1B: Marine; Microturbines, Turbochargers and Small Turbomachines; Steam Turbines, 2014
Int.J Automot. Technol., 2008
Most of hydrocarbon (HC) and carbon monoxide (CO) emissions from automotive DI Diesel engines are... more Most of hydrocarbon (HC) and carbon monoxide (CO) emissions from automotive DI Diesel engines are produced during the engine warm-up period and are primarily caused by difficulties in obtaining stable and efficient combustion under these conditions. Furthermore, the contribution of engine starting to these emissions is not negligible; since this operating condition is highly unfavorable for the combustion progress. Additionally,
Int.J Automot. Technol., 2008
One of the major goals of engine designers is the reduction of fuel consumption and pollutant emi... more One of the major goals of engine designers is the reduction of fuel consumption and pollutant emissions while keeping or even improving engine performance. In recent years, different technical issues have been investigated and incorporated into internal combustion engines in order to fulfill these requirements. Most are related to the combustion process since it is responsible for both fuel consumption and pollutant emissions. Additionally, the most critical operating points for an engine are both the starting and the warming up periods (the time the engine takes to reach its nominal temperature, generally between 80ºC and 90ºC), since at these points fuel consumption and pollutant emissions are larger than at any other points. Thus, reducing the warm-up period can be crucial to fulfill new demands and regulations. This period depends strongly on the engine cooling system and the different strategies used to control and regulate coolant flow and temperature. In the present work, the influences of different engine cooling system configurations on the warm-up period of a Diesel engine are studied. The first part of the work focuses on the modeling of a baseline engine cooling system and the tests performed to adjust and validate the model. Once the model was validated, different modifications of the engine coolant system were simulated. From the modelled results, the most favourable condition was selected in order to check on the test bench the reduction achieved in engine warm-up time and to quantify the benefits obtained in terms of engine fuel consumption and pollutant emissions under the New European Driving Cycle (NEDC). The results show that one of the selected configurations reduced the warm-up period by approximately 159 s when compared with the baseline configuration. As a consequence, important reductions in fuel consumption and pollutant emissions (HC and CO) were obtained.
Proceedings of the ASME Turbo Expo, 2010
ABSTRACT Turbocharging and turbocharger phenomena have been studied by many authors covering a wi... more ABSTRACT Turbocharging and turbocharger phenomena have been studied by many authors covering a wide range of subjects. One of these subjects, and objective of this work, is mechanical losses due to friction. Current work presents a methodology to characterize mechanical losses in small size turbochargers. Such methodology is based on low and constant operating temperature values for the turbine, lubricating oil, and compressor. In this way, a quasi-adiabatic operation of the turbocharger is achieved which allows separating friction power from heat transfer. The experiments performed have covered variations in turbocharger speed, lubricating oil pressure and temperature. Heat flows between turbine and compressor has been maintained as reduced as possible by means or the experiment conditions. The results obtained show satisfactory correlation between mechanical efficiency of the studied turbocharger and non-dimensional magnitudes.
Proceedings of the ASME Turbo Expo, 2010
ABSTRACT Turbocharging and turbocharger phenomena have been studied by many authors covering a wi... more ABSTRACT Turbocharging and turbocharger phenomena have been studied by many authors covering a wide range of subjects. One of these subjects, and objective of this work, is mechanical losses due to friction. Current work presents a methodology to characterize mechanical losses in small size turbochargers. Such methodology is based on low and constant operating temperature values for the turbine, lubricating oil, and compressor. In this way, a quasi-adiabatic operation of the turbocharger is achieved which allows separating friction power from heat transfer. The experiments performed have covered variations in turbocharger speed, lubricating oil pressure and temperature. Heat flows between turbine and compressor has been maintained as reduced as possible by means or the experiment conditions. The results obtained show satisfactory correlation between mechanical efficiency of the studied turbocharger and non-dimensional magnitudes.
Applied Thermal Engineering., 2014
ABSTRACT Heat transfer from the hot gases to the wall in exhaust systems of high-performance two-... more ABSTRACT Heat transfer from the hot gases to the wall in exhaust systems of high-performance two-stroke engines is underestimated using steady state with fully developed flow empirical correlations. This fact is detected when comparing measured and modeled pressure pulses in different positions in the exhaust system. This can be explained taking into account that classical expressions have been validated for fully developed flows, a situation that is far from the flow behavior in reciprocating internal combustion engines. Several researches have solved this phenomenon in four-stroke engines, suggesting that the unsteady flow is strongly linked to the heat transfer. This research evaluates the correlations proposed by other authors in four stroke engines and introduces a new heat transfer model for exhaust systems in two-stroke, high performance, gasoline engines. The model, which accounts for both the entrance length effect and flow velocity fluctuations, is validated against experimental measurements. Comparisons of the proposed model with other models are performed, showing not negligible differences in the scavenge process related parameters.
Applied Thermal Engineering., 2014
ABSTRACT Heat transfer from the hot gases to the wall in exhaust systems of high-performance two-... more ABSTRACT Heat transfer from the hot gases to the wall in exhaust systems of high-performance two-stroke engines is underestimated using steady state with fully developed flow empirical correlations. This fact is detected when comparing measured and modeled pressure pulses in different positions in the exhaust system. This can be explained taking into account that classical expressions have been validated for fully developed flows, a situation that is far from the flow behavior in reciprocating internal combustion engines. Several researches have solved this phenomenon in four-stroke engines, suggesting that the unsteady flow is strongly linked to the heat transfer. This research evaluates the correlations proposed by other authors in four stroke engines and introduces a new heat transfer model for exhaust systems in two-stroke, high performance, gasoline engines. The model, which accounts for both the entrance length effect and flow velocity fluctuations, is validated against experimental measurements. Comparisons of the proposed model with other models are performed, showing not negligible differences in the scavenge process related parameters.
ABSTRACT A specific study of the uncertainties of turbine power output measured in turbocharger t... more ABSTRACT A specific study of the uncertainties of turbine power output measured in turbocharger test benches is presented using the law of uncertainty propagation and the influence of the different terms that contribute to it is shown. Then, non-linear mixed integer mathematical programming algorithms used with the turbine power uncertainty expression become an essential tool to overcome the problem of selection new sensors to improve an existing test rig or to contribute to a new one. A method of optimisation is presented for two different scenarios: first, where the maximum cost is a constraint; second where the maximum uncertainty is a constraint and the total cost is minimised. When using a large transducers database, computational efforts may be reduced by solving the relaxed non-integer problem by means of sequential quadratic programming and then probing the ceilings and floors of the parameters to get an optimum approximation with low costs. A comparison between the linear uncertainty propagation model and Monte Carlo simulations is also presented, only showing benefits of the later method when computing high order statistical moments of the turbine power output probability distribution.
Energy, 2014
ABSTRACT The use of biodiesel fuels in diesel engines is gaining attention as a promising solutio... more ABSTRACT The use of biodiesel fuels in diesel engines is gaining attention as a promising solution to control CO2 emissions. Great research efforts have been carried out to identify the impact of biodiesel physical and chemical properties on engine systems and processes. Most of these investigations were performed in warm conditions, but the suitability of biodiesel for starting the engine at under-zero ambient temperatures has not widely evaluated. The surface tension and the viscosity of biodiesel fuels are higher compared to those of standard diesel and, in cold conditions, these differences become critical since the injection fuel rate is largely affected and consequently the combustion process can be deteriorated. In order to improve its flow characteristics at cold temperatures and make them more suitable for low temperatures operation, additives are used in biodiesel fuels. In this paper the suitability of different biodiesel fuels, with and without additives, for cold starting of DI (direct injection) diesel engines has been evaluated. The results have shown that the engine start-ability with pure biodiesel fuels can be largely deteriorated. However, using diesel/biodiesel blends the start-ability of the engine can be recovered with the additional benefit of reducing the opacity peak of the exhaust gases.
SAE Technical Paper Series, 2004
SAE Technical Paper Series, 2004
A lumped capacity heat transfer model has been developed and compared to measurements from a turb... more A lumped capacity heat transfer model has been developed and compared to measurements from a turbocharger operating on a 2.2L Diesel engine under steady and transient conditions ranging from 1000-3000rpm and 2-17bar BMEP. The model parameters have been estimated based on similar devices and this study quantifies the errors associated with this approach. Turbine outlet gas temperature prediction was improved with RMSE reduced from 29.5 o C to 13 o C. A sensitivity study showed the parameters of the heat transfer model influence gas temperatures by only ±4 o C but housing temperatures by up to 80 o C. Transient simulations showed how errors in the thermal capacitance also lead to errors. This study shows the importance of undertaking a full thermal characterisation and the need for accurate adiabatic maps in turbocharger simulations.
Nowadays turbocharging the internal combustion engine has become a key point in both the reductio... more Nowadays turbocharging the internal combustion engine has become a key point in both the reduction of pollutant
emissions and the improvement of engine performance. The matching between turbocharger and engine is difficult; some
of the reasons are the highly unsteady flow and the variety of diabatic and off-design conditions the turbocharger works
with. In present paper the importance of the heat transfer phenomena inside small automotive turbochargers will be
analyzed. These phenomena will be studied from the point of view of internal heat transfer between turbine and
compressor and with a one-dimensional approach. A series of tests in a gas stand, with steady and pulsating hot flow in the
turbine side, will be modeled to show the good agreement in turbocharger enthalpies prediction. The goodness of the
model will be also shown predicting turbine and compressor outlet temperatures. An accurate prediction of these
parameters is a key factor to make easier the design of intercooler and aftertreatment devices.
11th International Conference on Turbochargers and Turbocharging, 2014
11th International Conference on Turbochargers and Turbocharging, 2014
Multidisciplinary Journal for Education, Social and Technological Sciences, 2014
Multidisciplinary Journal for Education, Social and Technological Sciences, 2014
Volume 1B: Marine; Microturbines, Turbochargers and Small Turbomachines; Steam Turbines, 2014
Volume 1B: Marine; Microturbines, Turbochargers and Small Turbomachines; Steam Turbines, 2014
Int.J Automot. Technol., 2008
Most of hydrocarbon (HC) and carbon monoxide (CO) emissions from automotive DI Diesel engines are... more Most of hydrocarbon (HC) and carbon monoxide (CO) emissions from automotive DI Diesel engines are produced during the engine warm-up period and are primarily caused by difficulties in obtaining stable and efficient combustion under these conditions. Furthermore, the contribution of engine starting to these emissions is not negligible; since this operating condition is highly unfavorable for the combustion progress. Additionally,
Int.J Automot. Technol., 2008
One of the major goals of engine designers is the reduction of fuel consumption and pollutant emi... more One of the major goals of engine designers is the reduction of fuel consumption and pollutant emissions while keeping or even improving engine performance. In recent years, different technical issues have been investigated and incorporated into internal combustion engines in order to fulfill these requirements. Most are related to the combustion process since it is responsible for both fuel consumption and pollutant emissions. Additionally, the most critical operating points for an engine are both the starting and the warming up periods (the time the engine takes to reach its nominal temperature, generally between 80ºC and 90ºC), since at these points fuel consumption and pollutant emissions are larger than at any other points. Thus, reducing the warm-up period can be crucial to fulfill new demands and regulations. This period depends strongly on the engine cooling system and the different strategies used to control and regulate coolant flow and temperature. In the present work, the influences of different engine cooling system configurations on the warm-up period of a Diesel engine are studied. The first part of the work focuses on the modeling of a baseline engine cooling system and the tests performed to adjust and validate the model. Once the model was validated, different modifications of the engine coolant system were simulated. From the modelled results, the most favourable condition was selected in order to check on the test bench the reduction achieved in engine warm-up time and to quantify the benefits obtained in terms of engine fuel consumption and pollutant emissions under the New European Driving Cycle (NEDC). The results show that one of the selected configurations reduced the warm-up period by approximately 159 s when compared with the baseline configuration. As a consequence, important reductions in fuel consumption and pollutant emissions (HC and CO) were obtained.
Proceedings of the ASME Turbo Expo, 2010
ABSTRACT Turbocharging and turbocharger phenomena have been studied by many authors covering a wi... more ABSTRACT Turbocharging and turbocharger phenomena have been studied by many authors covering a wide range of subjects. One of these subjects, and objective of this work, is mechanical losses due to friction. Current work presents a methodology to characterize mechanical losses in small size turbochargers. Such methodology is based on low and constant operating temperature values for the turbine, lubricating oil, and compressor. In this way, a quasi-adiabatic operation of the turbocharger is achieved which allows separating friction power from heat transfer. The experiments performed have covered variations in turbocharger speed, lubricating oil pressure and temperature. Heat flows between turbine and compressor has been maintained as reduced as possible by means or the experiment conditions. The results obtained show satisfactory correlation between mechanical efficiency of the studied turbocharger and non-dimensional magnitudes.
Proceedings of the ASME Turbo Expo, 2010
ABSTRACT Turbocharging and turbocharger phenomena have been studied by many authors covering a wi... more ABSTRACT Turbocharging and turbocharger phenomena have been studied by many authors covering a wide range of subjects. One of these subjects, and objective of this work, is mechanical losses due to friction. Current work presents a methodology to characterize mechanical losses in small size turbochargers. Such methodology is based on low and constant operating temperature values for the turbine, lubricating oil, and compressor. In this way, a quasi-adiabatic operation of the turbocharger is achieved which allows separating friction power from heat transfer. The experiments performed have covered variations in turbocharger speed, lubricating oil pressure and temperature. Heat flows between turbine and compressor has been maintained as reduced as possible by means or the experiment conditions. The results obtained show satisfactory correlation between mechanical efficiency of the studied turbocharger and non-dimensional magnitudes.
Applied Thermal Engineering., 2014
ABSTRACT Heat transfer from the hot gases to the wall in exhaust systems of high-performance two-... more ABSTRACT Heat transfer from the hot gases to the wall in exhaust systems of high-performance two-stroke engines is underestimated using steady state with fully developed flow empirical correlations. This fact is detected when comparing measured and modeled pressure pulses in different positions in the exhaust system. This can be explained taking into account that classical expressions have been validated for fully developed flows, a situation that is far from the flow behavior in reciprocating internal combustion engines. Several researches have solved this phenomenon in four-stroke engines, suggesting that the unsteady flow is strongly linked to the heat transfer. This research evaluates the correlations proposed by other authors in four stroke engines and introduces a new heat transfer model for exhaust systems in two-stroke, high performance, gasoline engines. The model, which accounts for both the entrance length effect and flow velocity fluctuations, is validated against experimental measurements. Comparisons of the proposed model with other models are performed, showing not negligible differences in the scavenge process related parameters.
Applied Thermal Engineering., 2014
ABSTRACT Heat transfer from the hot gases to the wall in exhaust systems of high-performance two-... more ABSTRACT Heat transfer from the hot gases to the wall in exhaust systems of high-performance two-stroke engines is underestimated using steady state with fully developed flow empirical correlations. This fact is detected when comparing measured and modeled pressure pulses in different positions in the exhaust system. This can be explained taking into account that classical expressions have been validated for fully developed flows, a situation that is far from the flow behavior in reciprocating internal combustion engines. Several researches have solved this phenomenon in four-stroke engines, suggesting that the unsteady flow is strongly linked to the heat transfer. This research evaluates the correlations proposed by other authors in four stroke engines and introduces a new heat transfer model for exhaust systems in two-stroke, high performance, gasoline engines. The model, which accounts for both the entrance length effect and flow velocity fluctuations, is validated against experimental measurements. Comparisons of the proposed model with other models are performed, showing not negligible differences in the scavenge process related parameters.
ABSTRACT A specific study of the uncertainties of turbine power output measured in turbocharger t... more ABSTRACT A specific study of the uncertainties of turbine power output measured in turbocharger test benches is presented using the law of uncertainty propagation and the influence of the different terms that contribute to it is shown. Then, non-linear mixed integer mathematical programming algorithms used with the turbine power uncertainty expression become an essential tool to overcome the problem of selection new sensors to improve an existing test rig or to contribute to a new one. A method of optimisation is presented for two different scenarios: first, where the maximum cost is a constraint; second where the maximum uncertainty is a constraint and the total cost is minimised. When using a large transducers database, computational efforts may be reduced by solving the relaxed non-integer problem by means of sequential quadratic programming and then probing the ceilings and floors of the parameters to get an optimum approximation with low costs. A comparison between the linear uncertainty propagation model and Monte Carlo simulations is also presented, only showing benefits of the later method when computing high order statistical moments of the turbine power output probability distribution.
Energy, 2014
ABSTRACT The use of biodiesel fuels in diesel engines is gaining attention as a promising solutio... more ABSTRACT The use of biodiesel fuels in diesel engines is gaining attention as a promising solution to control CO2 emissions. Great research efforts have been carried out to identify the impact of biodiesel physical and chemical properties on engine systems and processes. Most of these investigations were performed in warm conditions, but the suitability of biodiesel for starting the engine at under-zero ambient temperatures has not widely evaluated. The surface tension and the viscosity of biodiesel fuels are higher compared to those of standard diesel and, in cold conditions, these differences become critical since the injection fuel rate is largely affected and consequently the combustion process can be deteriorated. In order to improve its flow characteristics at cold temperatures and make them more suitable for low temperatures operation, additives are used in biodiesel fuels. In this paper the suitability of different biodiesel fuels, with and without additives, for cold starting of DI (direct injection) diesel engines has been evaluated. The results have shown that the engine start-ability with pure biodiesel fuels can be largely deteriorated. However, using diesel/biodiesel blends the start-ability of the engine can be recovered with the additional benefit of reducing the opacity peak of the exhaust gases.
SAE Technical Paper Series, 2004
SAE Technical Paper Series, 2004